JPS61284082A - Positive resistance temperature coefficient heat generating body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a positive resistance temperature coefficient heating element (hereinafter referred to as a PTC heating element) useful as a heating appliance, a general heating device, and the like.

BACKGROUND OF THE INVENTION It has been known that a resistor composition in which conductive fine powder is dispersed in a crystalline polymer exhibits remarkable PTC characteristics, and a heating element with self-temperature control using this composition has been known. Attempts have been made to construct a The advantages of this method are that the shape of the resistor is excellent and any shape can be easily obtained, it has excellent flexibility, and the resistance value can be adjusted over a wide range. It has been used as a planar heating element and a long flexible heating element with low power density.

However, when a large power density is required, a heat equalizing plate is essential to make the temperature distribution of the heating element itself uniform. A PTC resistor 2 whose main component is a material in which conductive fine powder is dispersed in a crystalline polymer is closely adhered to an electrically insulating substrate 1 made of an alumina sintered body with good conductivity. Measures were taken such as providing a pair of electrodes 3a and 3b at both ends (Japanese Patent Publication No. 40161/1983).

Problems to be Solved by the Invention In such conventional high power density PTC heating elements, the heat equalizing plate is not fixed, and without the heat equalizing plate, local abnormal heat generation phenomenon due to voltage concentration will occur, and normal heat generation characteristics will not be maintained. will not be obtained. In addition, even if there is a heat soaking plate, the
There was a limit to the thermal conductivity of electrical insulating materials, and there was not enough margin to reach the voltage concentration limit. Furthermore, ceramic materials such as alumina sintered bodies are not flexible, have insufficient adhesion to objects to be heated, and are difficult to make large ones, so the size and shape of a heating element constructed in one piece is difficult to make. There were also limits. On the other hand, as an alternative material to ceramic-based heat equalizer plates, a heat equalizer plate made by laminating a high thermal conductivity metal plate such as aluminum and an electrically insulating plate such as polyester film has been devised, but it does not fully satisfy the dielectric strength characteristics. When the thickness of the electrical insulating plate is set to 1, it is difficult to obtain a heat equalization effect superior to that of the alumina sintered body, and a large power density cannot be obtained. In this way, the conventional high power density P
TC heating elements have a lot of problems caused by the soaking plate.
There was no room for further development.In order to solve this problem all at once, it was important to introduce a PTC heating element that did not need to rely on a heat equalizing plate. As a result of our studies focusing on this point, we found that the width of the area where the voltage concentration phenomenon occurs is several millimeters or less, and if we install a pair of electrodes within that area, we can reduce the voltage gradient between the electrodes. It was estimated that the heat distribution would be almost uniform. As a result of further investigation, it was found that if fine comb-shaped electrodes were provided on the surface of the PTC resistor, the area occupied by the electrodes would become considerably large, and there would be almost no effective heat generation area, making it impossible to obtain as high a power density. . As a solution, PT
As a result of introducing a voltage application method in the thickness direction of the C resistor and conducting repeated experiments, no extreme voltage concentration phenomenon was observed if the thickness of the resistor was 5 m++ or less. Also, the thickness is 1
In the case of small or smaller parts, 2.1 (e o a)
No abnormalities were observed during heat generation (eq temperature rise). From this result, it was concluded that the heat diffusion ability between the electrodes of a heating element in which electrodes were provided on both sides of a thin-walled PTC resistor having a thickness of 5 W or less was high, and that essentially no voltage concentration phenomenon could occur. However, although the phenomenon of destruction of the resistor due to voltage concentration did not occur, large deterioration occurred and heat transfer loss occurred, so it was found that the thickness of the resistor should be at least 3 mm or less, preferably 1 mm or less. . The heating element with this structure has a very simple structure and is free from the various constraints imposed by heat soaking plates, so it was expected to make a big leap forward in terms of performance, structure, and construction method. When we started concrete studies based on this conclusion, we found that there were many problems related to the withstand voltage characteristics of the PTC resistor composition, securing of insulation distance, terminal processing method, structure, processing method, etc., and the state was far from practical. The specific problems to be solved by the present invention will be explained below. Until now, the method of applying 1oOv to 20OV in the thickness direction of a thin-walled PTC resistor with a thickness of 3 mm or less, preferably 1 mm or less has been used because the distance between different electrodes is close, resulting in extremely small defects. Even if it were, it was predicted that withstand voltage breakdown would easily occur, and in the worst case, it would lead to burnout. One of the important factors contributing to the formation of such defects is the structure and processing method of the pair of oppositely polarized electrode end surfaces that are arranged in extremely close positions. Since the end faces of this pair of different polarity electrodes are separated by a distance of 3+a+ or less or 1M or less, it is easily assumed that the withstand voltage characteristics will be insufficient due to oxidation or the like. Also thin P
When a terminal is attached to the TC resistor itself, heat radiation from the terminal not only causes temperature unevenness with other parts of the resistor but also deteriorates thermal efficiency. Furthermore, since terminals are required on the front and back sides of the pair of electrodes, it is difficult to process the terminals after insulation treatment in post-processing, resulting in high assembly costs and problems in that productivity is not improved.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a thin positive temperature coefficient resistor having a composition in which conductive fine powder is dispersed in a crystalline polymer, and its thickness. The resistor comprises a pair of electrode bodies provided to apply a voltage in the direction, and the creepage distance along the outer surface of the resistor constructed between the end faces of the pair of electrode bodies is larger than the thickness dimension of the resistor. The resistor and the pair of electrode bodies are pasted together while setting the width dimension or positional relationship, and the electrode body protruding from the resistor is provided with a terminal portion, and is further covered with an electrically insulating material. A positive resistance temperature coefficient heating element is applied, which is constructed by forming a notch part in a part of the electrically insulating material so as to correspond to the terminal part.

For production The effect of this technical means is as follows.

In other words, if the thin-walled PTC resistor itself is interposed in a positional relationship that allows for sufficient creepage distance between the end faces of different polarity electrodes, and is integrally molded, safety can be achieved without using other electrically insulating materials on the end faces. can be secured. In addition, the electrode can be
By protruding beyond the width of the resistor and providing the terminal portion at an arbitrary position in that portion, the PTC resistor will not be adversely affected by pressure and heat due to soldering or the like.

Example Examples will be described below based on FIGS. 1 and 2.

In Fig. 1, 4 is a PTC resistor with a thickness of 1N or less,
The electrode 5a protrudes to the left of the width of the PTC resistor 4 by an amount larger than the area (particularly the width) where the terminal 6a is attached. −
The electrode 5b facing the blade protrudes to the right side from the width of the PTC resistor 4 by an amount equal to or larger than the area (particularly the width) when attaching the terminal 6b.

6b are bonded together in a positional relationship that allows them to be taken out in the same direction. This ensures that the creepage distance is at least twice the thickness of the PTC resistor 4.

Further, the electrical insulating layers 7a and 7b are made of heat-fusible electrical insulating tape, and are connected to the PTC resistor 4 and the electrode 5a.

5b is covered, and the electric insulating layer 7a is previously cut out at positions corresponding to the terminals ea and eb.

Next, FIG. 2 is a perspective view of a PTC heating element of the present invention continuously covered with heat-fusible electrical insulation tape. The notches 8a and 8b are processed using a hot roll at positions corresponding to the terminals 6a and 6b.

The structure shown in FIG.
The good thing is that the widths of terminals a and 5b are the same, and there is also a notch 8 in the electrical insulating tape so that terminals 5a and 6b can be easily taken out.
Since terminals a and sb are provided, terminal processing is easy. Effects of the invention As described above, the present invention provides a method for processing while ensuring creepage distance between the end faces of different electrodes. As shown, thin PT
Since the cross-sectional structure of the resistor and electrode portion of the heating element of the type in which voltage is applied in the thickness direction of the C resistor is determined from this viewpoint, the following effects are exhibited.

0) There are no concerns regarding the withstand voltage performance between the end faces of different electrodes, and a high-output PTC heating element can be obtained.

@) Since the terminal part is not in contact with the PTC resistor, there is little heat dissipation from the terminal, and temperature unevenness is less likely to occur. Furthermore, thermal deterioration due to soldering is less likely to occur.

(3) Productivity is high because the electrical insulator is notched to facilitate terminal processing.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a PTC heating element according to an embodiment of the present invention;
The figure is a perspective view of a PTC heating element according to an embodiment of the present invention, and FIG. 3 is a perspective view of a conventional PTC heating element. PTC resistor, 3a. 3b, 5a, 5b... Electrode, ea, eb...
...terminal, 7a, 7b...electrical insulating layer,
Ba, ab...notch part.

Claims (1)

[Claims] It consists of a thin positive temperature coefficient resistor whose main component is a composition in which conductive fine powder is dispersed in a crystalline polymer, and a pair of electrode bodies provided to apply a voltage in the thickness direction of the resistor. The width dimension or positional relationship between the resistor and the pair of electrode bodies is such that the creepage distance along the outer surface of the resistor configured between the end faces of the pair of electrode bodies is larger than the thickness of the resistor. A terminal portion is provided on the electrode body protruding from the resistor, and is further covered with an electrically insulating material, and a notch is formed in a part of the electrically insulating material so as to correspond to the terminal portion. A positive resistance temperature coefficient heating element having a configuration in which a portion is formed.